Running Head: Health Benefits of Happiness

Draft Date: October 29, 2010

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Health Benefits of Happiness

AbstractSeven types of evidence are reviewed that indicate that high subjective well-being (such as lifesatisfaction, absence of negative emotions, optimism, and positive emotions) causes better healthand longevity. For example, prospective longitudinal studies of normal populations provideevidence that various types of subjective well-being such as positive affect predict health andlongevity, controlling for health and socioeconomic status at baseline. Combined withexperimental human and animal research, as well as naturalistic studies of changes of subjectivewell-being and physiological processes over time, the case that subjective well-being influenceshealth and longevity in healthy populations is compelling. However, the claim that subjectivewell-being lengthens the lives of those with certain diseases such as cancer remainscontroversial. A number of studies indicate that positive feelings predict longevity and healthbeyond negative feelings. However, evidence suggests that intensely aroused or manic positiveaffect can be detrimental to health. Issues such as causality, effect size, types of subjective wellbeing, and statistical controls are discussed. Research is needed that examines in more depth thepsychological and physiological pathways by which various types of subjective well-beinginfluence health and longevity.

Health Benefits of Happiness

Happy People Live Longer: Subjective Well-Being Contributes to Health and LongevityWhen people list the characteristics of a good life, they are likely to include happiness,health, and longevity. Similarly, scholars such as Edgerton (1995) define good cultures as thosein which health and happiness flourish. In this paper we describe the evidence that subjectivewell-being (SWB) causally affects health and longevity. Interventions to raise SWB, as well asthe theories that explain why SWB affects physiology, are beyond the page limitations and scopeof this review.We describe the evidence that reveals that SWB causally influences both health andlongevity. By SWB we mean peoples evaluations of their lives, which can be judgments such aslife satisfaction, and evaluations based on feelings, including moods and emotions. When peoplefeel a sad mood or a joyful emotion it is because they evaluate something in their lives as goingwell or badly. Thus, SWB is a heterogeneous category that includes diverse phenomena rangingfrom optimism to low anger to work satisfaction. Through most of the paper we review measuresof diverse SWB concepts together as though they have similar effects on health, and onlyoccasionally mention when these effects diverge. The reason we conflate the different types ofSWB is that rarely have there been studies that differentiate and assess multiple types of SWB.Thus, we are not able to draw strong conclusions about which types of feelings are most relatedto health. Evidence has accumulated to show that positive and negative feelings haveindependent effects, but in most cases we have only an initial idea of how SWB concepts overlapor are independent in their effects on health. In a later section of the paper we describe theresearch that is needed to more finely dissect how various types of SWB influence health.Early research on SWB and health established a correlation between the two. But becausethe studies were largely cross-sectional, often with small samples of convenience, it was

Health Benefits of Happiness

impossible to determine the causal direction between SWB and health. However, the field hasnow progressed to the point where many forms of evidence are available. There are now anumber of converging lines of evidence based on diverse methodologies supporting theconclusion that SWB influences health and longevity.1. Long-term longitudinal (prospective) studies in which subject samples are followedover time, and initial levels of subjective well-being are related to later health andlongevity. These studies are most powerful when baseline levels of health are controlled,and SES is often controlled as well. Survival in ill populations has been studied, as wellas morbidity and mortality in initially healthy populations.2. Studies in which natural levels of SWB are related to specific physiological processesthat can affect health and longevity, as well as studies of when natural changes in SWBare related to changes in physiological measures.3. Studies in which moods and emotions are experimentally manipulated, and effects onphysiological variables that could affect health are assessed.4. Animal studies in which there is experimental control over the environment of theanimals, and physiological and health measures are assessed in animals likely to differ inSWB.5. Quasi-experimental studies in natural settings, in which natural events can beexamined for their effects on health outcomes.6. Experimental intervention studies in which treatments are administered that caninfluence peoples long-term SWB. The treatment groups are compared to control groupsin terms of both SWB and physiological measures.7. Studies on how quality of life factors such as pain and mobility are related to

Health Benefits of Happiness

subjective well-being.We describe examples of each of the types of evidence, as well as discuss issues such ascausality, effect size, methodological rigor, whether too much happiness can be detrimental tohealth, and whether there is a threshold effect for SWB. We focus on large-scale recent research,as well as studies that are diverse in the populations they sample and initial health-status. Wedescribe a number of systematic reviews and meta-analyses that are already available in specificareas, which provide more complete summaries of specific topics.Empirical Evidence by Methodological CategoryLongitudinal Prospective Studies of SWB, Health, and LongevityWe are fortunate that a number of reviews and meta-analyses are available on thepredictive power of SWB on health and longevity. Studies with very large sample sizes havebeen followed for a decade or more. In these impressively large studies SWB is usuallypredictive of mortality, controlling for initial health. Hemingway and Marmot (1999) found in areview of the literature that among studies that passed their quality filter, in 11 of 11prospective studies depression and anxiety predicted coronary heart disease in healthy people,and in six of six studies they predicted disease progression in those with cardiovascular disease.The authors suggest that the causal role of the mental states is further supported by human andprimate evidence on biological and behavioral pathways mediating these effects.Lyubomirsky, King, and Diener (2005), in a meta-analysis of longitudinal studies, foundan effect size of .18, indicating the standard deviation differences in health outcomes for lowversus high SWB individuals. Similarly, Howell, Kern, and Lyubomirsky (2007) reviewed 49prospective studies testing the predictive power of long-term well-being and ill-being, and foundan overall effect size of .14 for longevity, comparing high and low SWB subjects.

Health Benefits of Happiness

Chida and Steptoe (2008) conducted a meta-analysis of the prospective studies examiningthe association between positive well-being and mortality in both healthy and diseasedpopulations. Positive psychological well-being was related to lower mortality in both healthy anddiseased populations, independently of negative effect. Positive moods such as joy, happiness,and energy, as well as characteristics such as life satisfaction, hopefulness, optimism, and senseof humor were associated with reduced risk of mortality in healthy populations, and predictedlongevity, controlling for negative states. Positive states were associated with reduced death ratesin patients with HIV and renal failure. In the healthy population studies, higher quality studiesyielded evidence of greater protective effects. In the disease population studies the protectiveeffects were greater when baseline disease and treatment were controlled.Rugulies (2002) reported a meta-analysis of 11 studies examining whether depressionpredicts coronary heart disease. It was concluded that depression predicts cardiovascular diseasein initially healthy people, with a greater risk for clinical depression than for depressed mood(risk ratios of 2.69 and 1.49, respectively). Studies that excluded participants with a suspiciousEEG at baseline, and those with cardiac events early in the follow-up period showed a risk ratioof 1.51.Williams and Schneiderman (2002) argue that there is now strong evidence that SWB ispredictive of cardiovascular disease is healthy populations. They also conclude that SWB ispredictive of cancer incidence and survival, although the evidence is limited. Pressman andCohen (2005) review evidence suggesting that positive affect is associated with physical healthand longevity in normal populations, but concluded that the evidence is mixed for positive affectpredicting survival in those with existing disease. Thus, a number of literature reviews and metaanalyses all conclude that SWB predicts health and longevity in healthy populations.

Health Benefits of Happiness

In Table 1 we present examples of prospective studies in the area of SWB and longevity.The table is designed to give an idea of the extent, range, and diversity of the findings. Several ofthese studies have overlapping samples, but different measures and time periods. As can be seen,SWB, especially in the form of positive affect, has been found to be associated with mortalityand longevity in many samples (including very large ones), in a number of different nations, andcontrolling for potential confounds such as initial health and SES. The results leave little doubtthat subjective well-being in general predicts longevity. In some studies SWB was associatedwith longevity only in a subset of the sample, such as only in men or only for one type of SWB,and such differences provide leads for future research.A current question without a definitive answer is whether SWB can improve peopleschances of surviving existing illnesses. The results on survival are mixed, with some studiesshowing that high SWB increases likelihood of survival from certain illnesses, and other studiesshowing no effect. Pressman and Cohen (2005) suggested that positive states might bedetrimental to the health of people with advanced diseases with a poor short-term prognosis,while being beneficial to those with diseases that have a better prospect of long-term survival. Inaddition, in a few cases such as asthma, highly aroused positive states might be detrimental,triggering attacks.In a review of prospective studies, Suls and Bunde (2005) conclude that Negativeemotions, especially depression and anxiety, appear to be related to increased cardiovasculardisease risk in healthy samples, but it is unclear whether these emotions have an independentand/or additive effect . . . . and with the possible exception of depression, that studies ofpopulations with known diseases do not present as strong or consistent a role for negativeemotions in CHD progression. (p. 292). The authors suggest that negative emotions may play a

Health Benefits of Happiness

stronger role in cardiovascular disease development than in progression once it is present.

Veenhoven (2008) also concluded that happiness predicts longevity in health populations butdoes not cure illness in sick populations.One complication in interpreting SWB effects is that in research controlling for baselinehealth, the researchers might actually be studying whether SWB has a greater influence in laterlife than in earlier life because even at Time 1 SWB levels are likely to already have had animpact. However, there are studies in which high SWB clearly has been found to have positiveeffects on those with existing diseases. For example, Scheier et al. (1989) found that postsurgicalphysical recovery among coronary bypass patients was quicker for optimists, as was resumptionof normal activities after hospital discharge.Positive states are not likely to help people overcome any and all illnesses. Even ifpositive states boost peoples immune systems and have other desirable physiological benefits,these might not be sufficient to vanquish certain very serious illnesses such as rabies orpancreatic cancer. Although a positive attitude can help a persons quality of life when they havea fatal illness, no amount of SWB can overcome some diseases. Thus, we must search for theconditions under which SWB can benefit the health of those with specific diseases.In Table 2 we present prospective studies on SWB predicting later health and disease.The results are consistent in indicating that SWB predicts disease, although the findings aremuch clearer and complete for cardiovascular disease than other illnesses. These prospectivestudies indicate a payoff for healthy populations, and a weaker but positive effect in somediseased populations. The evidence that positive SWB helps those with diseases such as cancerappears to be mixed, with uncertain overall support at this time.

Health Benefits of Happiness

Even the impressively large and long-term prospective studies among healthy populationscannot definitively establish causality because initial unmeasured states of health and resourcescould produce the association between SWB and later health and longevity. Many of theplausible variables have been controlled in the existing studies, but the possibility remains ofother potential uncontrolled explanatory factors. Thus, we must also consult other types ofevidence.Human Studies of SWB, Physiology, and HealthResearchers have studied how both short- and long-term negative and positive affect areassociated with physiological indicators in natural settings. Moods and emotions are associatedwith cardiovascular indicators (Smyth et al, 1998; Steptoe, ODonnell, Bodrick, Kumari, &Marmot, 2007). Raikkonen, Matthews, Flory, Owens, and Gump (1999) found that pessimistshave higher blood pressure levels. Steptoe, Wardle, and Marmot (2005) found that positive affectin middle-aged men and women were associated with reduced neuroendocrine, cardiovascular,and inflammatory activity. The fibrinogen response to stress was smaller in happier individuals.Positive affect assessed periodically during the day was related inversely to heart rate assessedby ambulatory monitoring during the day. Importantly, the effects were independent of distress.Blood pressure elevations during mental stress can be substantial, equaling those of exercise(Rozanski, Blumenthal, & Kaplan, 1999).Fredrickson and Levenson (1998) found that films eliciting positive emotions speededrecovery from cardiovascular activation after subjects had viewed a fear-eliciting film.Brummett, Boyle, Kuhn, Diegler, and Williams (2009) found that positive feelings wereassociated with lower blood pressure reactivity during sadness recall but not during anger recall,and were related to more epinephrine, as well as lower cortisol rise after waking. Ostir, Berges,

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Markides, and Ottenbacher (2006) found in a sample of Mexican-Americans aged 65 and olderwho were not on hypertensive medication that positive affect was associated with lower bloodpressure. After adjusting for relevant risk factors, positive affect continued to be significantlyassociated with lower diastolic blood pressure.The physiological changes resulting from moods are, in turn, related to changes in health.For instance, many studies have shown that various forms of negative affect from stress toanxiety to depression are associated with deleterious changes in the cardiovascular system(Howell, Kern, & Lyubomirsky, 2007). Rozanski, Blumenthal, and Kaplan (1999) describedevidence showing that mental states such as stress and anger induced in the laboratory result inischemia, with some types of stress being worse than others. Those experiencing ischemia in thelaboratory are more likely to manifest this during the ECG monitoring of daily life events aswell. Gullette et al. (1997) found that transitory negative emotions increased the relative risk ofischemia, as assessed with ambulatory ECG monitoring. Aboa-Ebule et al. (2010) followedpeople after a myocardial infarction and found a higher incidence of future cardiovasculardisease for people with high job strain.Chida and Steptoe (2008) conclude that positive psychological states may influenceinflammatory and coagulation factors, which are involved in cardiovascular disease. The lowerlevels of cortisol associated with positive states may reduce the risk of metabolic, cardiovascular,and immune diseases. Chida and Steptoe note that the protective effects of SWB on mortalitypersist even when the behavioral factors are controlled, suggesting that physiological mediatorsare involved.Paterniti et al. (2001) followed subjects for four years and found that those with initiallyhigh trait anxiety had greater thickening of carotid arteries over the period than those low inanxiety, and this occurred for both men and women. Sapolsky (2005) reviews evidence

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indicating that chronic stress is related to hypertension and adult-onset diabetes. Smith, Glazer,Ruiz, and Gallo (2004) review evidence indicating that anger and hostility are related not only tothe initial development of cardiovascular disease, but also to disease progression, as indicated bystudies of ischemia and atherosclerosis. A similar conclusion was reached in a meta-analysis byMiller, Smith, Turner, Guijarro, and Hallet (1996). Marsland, Prather, Petersen, Cohen, andManuck (2008) found that hostility and trait negative affect were predictive of inflammatorymarkers.Kiecolt-Glaser, McGuire, Robles, and Glaser (2002) provide an excellent review ofphysiological pathways through which emotions can influence bodily reactions. Negativeemotions enhance the production of proinflammatory cytokines, for example. Inflammation inturn has been linked to certain cancers, Alzheimers disease, arthritis, frailty, osteoporosis, andcardiovascular disease. Furthermore, negative feelings can contribute to delayed wound healingand infection.SWB has not only been related to cardiovascular health, but also to immune functioning(Howell, Kern, & Lyubomirsky, 2007). Costanzo et al. (2004) found that angry individuals had aweaker immune response to a vaccine, whereas those high in optimism had a stronger response(see also Kohut, Cooper, Nickolaus, Russell, & Cunnick, 2002). Similarly, Byrnes et al. (1998)found immune decrements in pessimistic versus optimistic women with HIV. Herbert and Cohen(1993) in a meta-analysis found that stress predicted lower values of immune parameters.Interestingly, objective stress was a better predictor than self-reported stress, and this pattern wasreplicated by Segerstrom and Miller (2004). Rosenkranz et al. (2003), building on earlier workby Davidson, Coe, Dolski, and Donzella (1999) found that negative affect as indexed by bothright prefrontal brain activation and startle-response predicted worse immune functioning.

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Marsland et al. (2006) followed healthy graduate students after a Hepatitis B vaccination.Dispositional positive affect predicted a stronger antibody response, and was largely independentof negative affect and optimism. Marsland, Pressman, and Cohen (2007) suggest that bothpositive and negative mood states can heighten immune responding, but that only long-termpositive emotion traits predict greater immune competence independently of negative affect.Segerstrom and Sephton (2010) found among first-year law students that changes in bothoptimism and positive affect across time were associated with changes in immune responses. Theeffects of each persisted when controlled for the other, but were reduced to about half of theirformer strength. This dynamic relation over time suggests that increasing positive affectstrengthens immunity, and that the relation between the two is not due simply to inborntemperament or stable differences in life circumstances.Moods and emotions also can influence the reproductive system. For example, a recentstudy on fertility in women indicated that stress decreases the likelihood of pregnancy in thoseseeking to have children (Buck et al., in press). The authors suggested that perhaps stress reducedfecundity through a sympathetic medullar pathway.An intriguing recent finding is the effect of low SWB on telomere shortening, which canbe associated with physical ailments due to increased likelihood of errors during cell replication.Shorter telomeres resulting from negative emotions could cause health issues in a variety ofdifferent bodily systems because of the greater probability that new cells will contain replicationmistakes, and therefore not have fidelity to the original genetic code. Lung, Chen, and Shu(2007) found that major depressive disorder, as well as age, predicted shorter telomere length.Damjanovic et al. (2007) found that Alzheimers patient caregivers experienced both depressivesymptoms and had shorter telomere length compared to controls. Tyrka et al. (2010) found that

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childhood maltreatment predicted shorter telomere length in adults. Epel et al. (2004) found thatboth perceived stress and chronic stress were related to shorter telomere length. Cherkas et al.(2006) analyzed adult female twin pairs, and discovered that low SES predicted shorter telomerelength beyond the effects of smoking, obesity, and lack of exercise. Thus, negative feelings couldproduce widespread premature aging in diverse bodily systems, with the grater likelihood ofhealth problems ensuing.Positive affect also is associated with protective psychosocial and behavioral factors suchas greater social connectedness, perceived social support, optimism, and preference for adaptivecoping responses, as well as a grater probability of performing health behaviors. Cross-culturalresearch has documented associations with exercising regularly, not smoking, and prudent diet(Steptoe, Dockray, & Wardle, 2009). Grant, Wardle, and Steptoe (2009) studied a large sample ofindividuals in 21 nations and found that high life satisfaction was associated with not smoking,physical exercise, a healthier diet, and using sun protection. Thus, positive affect, in addition toits physiological outcomes, also may be part of a broader profile of psychosocial resilience thatreduces the risk of adverse physical health behaviors, which can influence multiple bodilysystems.It appears that short-term emotions, both negative and positive, sometimes produceadaptive bodily responses, whereas long-term negative states can produce deleterious patterns(Segerstrom & Miller, 2004). Short-term changes in mood and physiology might reflect adaptiveresponses to challenges, and are not necessarily indicative of pathology, whereas chronic stressand depression can create physiological responses that are harmful.In sum, moods and emotions are consistently found to be associated with biologicalmeasures such as blood pressure, cortisol, and inflammation, as well as indicators of disease suchas artery wall thickening. Importantly, the relation of positive feelings with physiology occur in

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addition to the effects of negative feelings and depression, suggesting that positive affect mayhave distinctive biological correlates that can benefit health.Experimental Manipulations of Emotions Combined with Physiological Outcome MeasuresIn experimental studies positive and negative moods are induced in some subjects andcontrasted with neutral or other mood conditions in terms of health-relevant physiologicalmeasures. For instance, Robles, Brooks, and Pressman (2009) conducted an experiment in whichstress versus no stress was induced in two groups, and skin recovery time after tape-strippingwas measured. Trait positive emotions predicted quicker skin barrier recovery in the stressinduced group, showing the buffering effect of positive feelings on the effects of stress on skinbarrier recovery. Fredrickson, Mancuso, Branigan, and Tugade (2000) carried out an experimentin which subjects who were exposed to a positive mood induction showed quicker cardiovascularrecovery after a stressful task than subjects who were exposed to neutral or negative moodinductions.In a controlled experiment (Kiecolt-Glaser et al., 2005) married couples were givenblister wounds and assigned to a marital disagreement condition and to a social supportinteraction during two consecutive stays in a hospital setting. Following the marital conflictcondition, subjects had slower wound healing and lower cytokine production than they showedin the social support condition. In addition, couples who were generally higher in hostilityshowed slower wound healing than low hostile couples, as well as more tumor necrosis and apoorer immune response.Several reviews and meta-analyses indicate that emotional states induced experimentallyare associated with health-relevant physiological outcomes. Lyubomirsky, King, and Diener(2005) found an effect size of .38 between experimentally induced positive affect and physical

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outcomes such as immune function and cardiovascular reactivity. Pressman and Cohen (2005)reviewed both experimental and naturalistic ambulatory evidence showing that positive emotionsare related in the preponderance of studies to immune, endocrine, and cardiovascular parameters.Howell, Kern, and Lyubomirsky (2007) reviewed 139 experimental studies testing the impact ofwell-being on health-relevant physiological outcomes. Inductions of well-being and ill-being ledto positive biological outcomes and negative biological outcomes, respectively. The impact ofwell-being was much stronger for immune response and pain tolerance, and nonsignificant forcardiovascular reactivity, although positive emotions produced a significant drop in cortisol. Thestrongest effect size they reviewed was between transient positive emotions and sIgA antibodyproduction.Not all research has found physiological reactions in response to mood inductions (e.g.,Kiecolt-Glaser et al., 2008), and therefore we need to explore in more depth what types ofphysiological responses occur in response to what levels and types of moods and emotions. Insum, a large number of experimental studies reveal that moods and emotions can influencehealth-relevant physiological responses with moderately strong effects in some cases, although insome cases no physiological effects are found for short-term mild moods.Animal StudiesAnimal studies reveal that conditions likely to cause stress have a negative impact onhealth. Manuck, Kaplan, and Clarkson (1983) found that socially stressed monkeys developedmore extensive coronary artery atherosclerosis than unstressed controls. Capitanio and Lerche(1998) found that psychosocial experiences such as isolation are likely to produce a stressfulstate that is associated with shorter survival in SIV-infected monkeys. Salak-Johnson and

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McGlone (2007) review animal studies on the relation of stress and immunity and found thatchronic stress caused by psychosocial factors suppresses the immune systemRozanski, Blumenthal, and Kaplan (1999) describe animal research showing that theventricular fibrillatory threshold is substantially reduced by a stressful environment. The authorsconclude that . . . these studies show that behavioral stress . . . significantly decreases theelectrical stability of the heart (p. 2206). They further conclude, based on both human andanimal studies, that stress influences blood coagulation. Von Borell (1995) reviewed evidenceshowing that stress in pigs can cause elevated cortisol and suppresses immune activity, and thatsocial stress can decrease disease resistance in chickens.Barnett and Hemsworth (1990) describe studies indicating that the type of housingprovided to pigs, which can influence levels of stress, influences plasma glucose, as well asdecreased responsiveness of the immune system. Enteric bacteria may grow more rapidly instressed animals (Freestone & Lyte, 2010). Tethered pigs show greater basal metabolism thangroup-housed pigs. Both housing systems and threatening human behavior can elevate plasmafree corticosteroids, with negative results for pregnancy, growth, and immune strength.Boissy et al. (2007) review methods for assessing positive emotions in animals, includingthrough the observation of certain behaviors such as play, affiliation, and vocalizations, andthrough certain environmental circumstances such as increasing or decreasing rewards. Althoughfew studies have yet been published on positive feelings in animals, several intriguing findingsare reviewed by Boissy et al. They review studies suggesting that both negative and positivepsychosocial experience in pigs influences health. For example, pigs that learned a mastery taskto obtain reward, giving them some control over their environment, later showed quicker woundhealing and carcass quality (Ernst, Tuchscherer, Kanitz, Puppe, & Manteuffel, 2006).

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Social factors can have a positive effect on animal health. Cohen, Kaplan, Cunnick,Manuck, and Rabsin (1992) found increased immune response in animals that are moreaffiliative, possibly due to the stress-buffering effect of affiliation. Detillion et al (2004) showthat positive social interaction improves wound healing in hamsters. Craft et al. (2006) foundthat social interaction among mice post-stroke helps decrease stroke-induced neuronal death.Short-term stress can lead to adaptive changes in behavior and physiology that may notbe detrimental to health. However, the adaptation processes to long-term stress can bedetrimental to health because it calls for diverting resources from bodily maintenance, growth,and reproduction (Barnett & Hemsworth, 1990). In the short run, diverting resources in responseto threats makes evolutionary sense because animals then have more resources to devote toemergency behaviors, thus potentially saving their lives. However, in the long-run such diversionof bodily resources can lead to a failure to reproduce and repair bodily damage.Quasi-Experiments of Natural Events and Health OutcomesQuasi-experimental studies suggest that emotional events and disasters are associatedwith cardiovascular and immune changes, and can trigger deaths in those who are affected by adisaster even though not directly killed by it, probably in vulnerable populations. Rozanski,Blumenthal, and Kaplan (1999) review evidence showing that death spikes during the first monthafter bereavement, with greater than a two-fold increase in mortality for men and a three-foldincrease for women, and then returns to normal levels. Similarly, they report that there was aspike in deaths in Israel on the first day of missile strikes during the Gulf War of 1991, unrelatedto direct deaths from the strikes. On the day of the 1994 earthquake in Los Angeles, deaths roseto five times the rate of the week before. Even observing exciting sports events seems to be ableto trigger cardiac deaths (Carroll, Ebrahim, Tilling, Macleod, & Smith, 2002).

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Evidence also connects major stressful events to physiological changes. Rozanski,

Blumenthal, and Kaplan (1999) described a quasi-experimental study in which blood sampleswere taken from hypertensive patients before and after an earthquake. The quake inducedtransient elevations in blood pressure and viscosity, and these parameters returned to baselineafter four to six months. Marucha, Kiecolt-Glaser, and Favagehi (1998) assessed wound healingtime in dental students during the summer vacation and again during the first examinations of theyear. Students took on average three days longer to heal a small, standardized wound during theexaminations, and interleukin messenger RNA was 68% lower during the tests. The pattern offindings held for all 11 students in the study.Work stress has been related to systematic differences in cortisol (Schlotz, Hellhammer,Schulz, & Stone, 2004). People with work overload and worry showed higher cortisol responseat awakening and higher mean cortisol levels on weekdays but not weekends. Those reportingthe most work stress showed the greatest weekend-weekday differences in waking cortisolresponse.It is challenging to find single positive events that clearly benefit health. AlthoughBerthier and Boulay (2003) found deaths dropped in France when they won the World Cup, astudy by Katz et al. (2005) found an increase in cardiac arrests in Switzerland during the WorldCup. However, positive responses to sporting competitions can be confounded by behaviors suchas alcohol consumption and smoking, failure to comply with medical regimens, a decrease inphysical activity, and stress during the event. Thus, winning sporting events may not be a clearindicator of the effects of positive emotions. Furthermore, it is possible that the highly arousedpositive emotions arising from exciting events can trigger cardiovascular problems in vulnerableindividuals. It could be that single exciting discrete positive events are not as beneficial to health

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as are circumstances that produce long-term positive moods and emotions, which are usually of aless aroused type.Interventions that Alter Long-Term SWB with Health Outcomes AssessedA number of interventions have led to changes in physiological functioning. Schneider etal. (1995) found that transcendental meditation and progressive relaxation treatments bothreduced blood-pressure over a 3-month follow-up period, compared to a control group. Davidsonet al. (2003) found increased positive affect and left-sided anterior brain activation in meditatorscompared to wait-list controls, and these were accompanied by increases in antibodies to fluvaccine. Gidron, Davidson, and Bata (1999) found that a hostility-reduction intervention in menwith cardiovascular disease led to significantly lower diastolic blood pressure compared tocontrol group participants, after a two-month period. Reductions in hostility were correlated .47with reductions in resting diastolic blood pressure.The physiological outcomes shown in the experimental intervention studies are capableof influencing health-relevant measures. Burton and King (2003) studied the health benefits ofwriting about intensely positive experiences or a control topic. Those who wrote about positivetopics had fewer health center visits for illness during the following three months. Holden-Lund(1988) assigned patients undergoing cholecystectomy to one of two treatments, either a controlcondition or a relaxation with guided imagery condition. Those in the treatment conditionexhibited less wound inflammation and redness than the control subjects.Friedman et al. (1986) conducted an experimental intervention with patients who havesuffered myocardial infarction, and who were observed for about five years after receivingcounseling. Ninety-five percent of patients exhibited Type A behavior at the beginning of thestudy, varying from moderate to very severe. There was a no-treatment control group, a cardiac

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counseling group, and a cardiac plus Type-A counseling group. The recurrence rate of MI was12.9% in the cardiac plus Type-A counseling group, 28.2% in the control group, and 21.2% inthose receiving cardiac counseling only. Those who received Type-A counseling in addition totraditional cardiac counseling were less likely to die in the final years of the study.An intervention that suggests the effects of psychosocial well-being on longevityoccurred in a study of palliative care for patients with metastatic lung cancer. Temel et al. (2010)conducted an experiment in which one group of terminal cancer patients received palliative careearlier than typical, compared to the control group which received palliative care at the standardtime. The early-care patients had fewer depressive symptoms and lived almost three monthslonger than the 9-month average survival time in the control group.Schneiderman, Antoni, Saab, and Ironson (2001) concluded that the evidence thatinterventions have an impact on mortality and morbidity are not definitive, and depend on theparticular disease state. Larger scale clinical trials on interventions with specific disease groupsare needed to provide more certain conclusions. There are initially promising results for Type Ainterventions for health outcomes among cardiology patients, and psychosocial interventions forcancer patients. Psychosocial interventions can decrease distress and may improve immunefunction in HIV/AIDS patients. The intervention evidence is promising and large-scaletreatment studies are now needed.Thus far, clear support that psychosocial interventions can alter survival in patients withmetastatic cancer is limited. Chow, Tsao, and Harth (2004) conducted a meta-analysis ofexperimental studies analyzing the effects of psychosocial interventions such as social supportfor the survival of patients with metastatic cancer over periods of 1 to 4 years (eight trialsinvolving 1,062 patients). The authors found no effects of the interventions on survival time,

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although they do reported that contamination of the control groups with natural social supportis quite possible, and that most the studies they reviewed had small samples and poorcompliance. Thus, although there is promising evidence that efforts to raise well-being and lowernegative states such as hostility can reduce heart disease and death, evidence that psychosocialinterventions can help people with metastatic cancer is not yet convincing.There are a number of hurdles for intervention studies. One is to actually reduce longterm negative affect and increase long-term positive affect. Rozanski, Blumenthal, and Kaplan(1999) conclude that in some studies where psychosocial interventions have failed to producehealth outcomes, in fact the interventions produced no reduction in distress. Furthermore, controlgroup participants may have substantial psychosocial resources, making it difficult to raise theSWB of the experimental group above the background condition of the control group. It might bethat interventions are most likely raise the SWB of individuals who are deficient in psychologicaland social resources. Existing studies indicate that interventions can in some cases affectphysiology and health. The challenge now is to determine which interventions will reliablyinfluence SWB, and in turn affect which disease states.SWBs Impact on Patients Quality of Life and PainIn a review of the pain and well-being literature, Pressman and Cohen (2005) found thatin most studies positive emotions were related to lower pain or greater tolerance for pain.Similarly, Howell, Kern, and Lyubomirsky (2007) found in a meta-analysis a strong associationbetween SWB and pain tolerance. For instance, Bruehl, Carlson, and McCubbin (1993) in anexperimental paradigm found that positive mood induction participants reported less pain tofinger pressure pain, and greater finger temperature recovery than controls. Willmarth (1999)hypnotically induced a positive mood and found decreases in self-reports of pain in chronic pain

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patients. Tang et al. (2008) found that an induction of depressed mood resulted in higher painratings at rest and lower pain tolerance, whereas induced happy mood resulted in the oppositepattern.

Fasman (2009) found that fibromyalgia patients had higher levels of pain thresholds formild and moderate pain with higher levels of trait positive affect. Strand et al. (2006) studiedrheumatoid arthritis patients over eight weeks. High positive affect served to mitigate negativeaffect during periods of high pain. Master et al. (2009) found that women reported less pain toheat stimuli when looking at pictures of their partner. Thus, the effects of positive affect on painare supported both in experimental laboratory studies and in research in natural settings, as wellas with both self-report and pain tolerance as dependent measures.Besides pain, high SWB can influence other aspects of the quality of life of patients.Positive emotions predicted recovery of greater functional status among stroke patients aged 55and older after three months (Ostir, Berges, Ottenbacher, Clow, & Ottenbacher, 2008). Kung etal. (2006) found, however, that optimism was more strongly associated with quality of life insurvivors of thyroid cancer than those with head and neck cancer, in that the head/neckassociations were no longer significant after controlling for age, sex, and disease stage. Studiesin the Table showed that high SWB is associated with greater functional status and mobility.Thus, SWB helps not only health but quality of life when a person is sick.IssuesCausalityHow strong is the case that high SWB causes better health and longevity rather thansimply predicts them? Prospective studies in which SWB precedes and predicts health andlongevity, controlling for baseline health, make plausible the claim that SWB influences health.

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Despite the impressively large studies showing that SWB predicts health outcomes, the issue ofunmeasured third variables remains. For instance, prenatal nutrition could conceivably influenceboth later SWB and health, and create an association between the two even in the absence ofcausality. Another explanation is that early home environment might influence both later SWBand health, and create the predictive association between the two. Miller and Chen (2010) foundthat a harsh family childhood environment was associated with a proinflammatory responsestyle, and it is plausible that such a childhood also might predispose a person to lower SWB.Thus, third-variable explanations cannot be entirely ruled out based on the longitudinal data, andadditional potential explanatory variables should be assessed and analyzed in future studies.Fortunately, additional methodological approaches provide corroborative andcomplementary evidence to suggest that SWB causally influences health. Experimental studieswith animals in which one condition is exposed to a negative or positive environment, indicatethat environmental conditions, which are likely to induce negative or positive feelings, influencehealth. Quasi-experimental interventions with humans in which propinquity to emotional eventsis accompanied by physiological responses and higher death rates add to the evidence forcausality.Evidence that SWB can influence physiology and health also comes from humanexperimental studies combined with studies in which mood changes are tracked over time andphysiological changes are monitored. There is substantial evidence that moods and emotions areassociated with physiological responses, as well as with health outcomes. When people arefollowed over time changes in their moods are usually tracked by changes in immune andcardiovascular measures. When moods are experimentally induced physiological changes areoften seen. These studies indicate that it is not simply long-term person factors such as SES,

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childhood nutrition, personality, or early family environment that cause the SWB and health link,because the health-relevant physiological changes track up and down with moods and emotionsover time. For example, when couples argue they show physiological responses that can bedetrimental to health in the long-term, compared to the responses they show when the supporteach other. Finally, long-term chronic moods and emotions such as depression are related tophysiological patterns that signal disease progression, such as thickening of artery walls. Thesestudies leave little doubt that peoples emotional responses are often accompanied by myriadphysiological changes that over time are likely to cause health problems.A final type of evidence for the causal role of SWB on health comes from randomizedcontrolled intervention studies in which conditions designed to enhance SWB are compared tocontrol conditions. In a number of studies activities that enhance SWB such as meditation havebeen shown to cause beneficial physiological responses. Although more intervention studies areneeded, the initial findings are promising.In sum, a strong case, but perhaps not an airtight case, can be made that SWB causallyinfluences health and longevity. Although there are limitations in each type of evidence, studiesconverge from a number of complementary methodologies, including experiments and quasiexperiments, to form a compelling picture.Ultimately causality is a theoretical issue that must be understood within a causalconceptual structure of a dynamic system. Single formal experiments shed some light on whetherA causes B, but they are limited in terms of understanding the full causal system at work. Forexample, experiments tend to be focused on one or two independent variables, and thereforeusually provide little insight into the full system that must be in place for the causal sequence tooccur. Usually A is sufficient to cause B only if a set of additional circumstances are already in

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place. Furthermore, experiments usually demonstrate that a causal sequence can occur, but notwhether it in fact does cause the outcomes the natural world. In other words, experiments explorewhat can happen more than what does happen. In addition, the structure of what causes B can beexplored at various levels of analysis and in ever-finer detail. Furthermore, in most experimentsthere are a large number of subjects who are not affected by the experimental treatment.Although these are sometimes dismissed as due to the probabilistic nature of the phenomenon, infact they are usually due to our lack of complete understanding of the causal system involved.Experiments are an important method helping to explore causality, but other methods areessential to fully understand the causal system. In complex systems causality is not so muchproven by a definitive experiment as it is developed over time as a theoretical model isdeveloped, tested, and refined by a variety of complementary methodologies, which usuallyinclude randomized controlled trials. This is the type of evidence that has now been accumulatedfor the SWB and health connection. Furthermore, several promising conceptual models exist forunderstand the effects of SWB on health (Davidson, 2004; Kiecolt-Glaser, McGuire, Robles, andGlaser, 2002; Sapolsky, 2005).Priorities for Future ResearchThere are several priorities for future research in order to fully understand the associationof SWB and health. There is now little doubt that SWB is associated with longevity and certainhealth outcomes, but there are many remaining important and interesting questions to beanswered.1. Processes. What are the psychological processes that influence physiological changesrelated to health? How do feelings and thoughts lead to physiological changes in the immune,cardiovascular, and other bodily systems? How does SWB interact with social support to

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influence health? Social relationships have been found to have a strong association withmortality, and in fact show a larger effect on longevity than factors such as physical activity,body-mass index, air pollution, and drug treatment for hypertension (Holt-Lumstad, Smith, &Layton, 2010). Only smoking and smoking cessation rival the social quality variables inpredicting longevity. Thus, an important avenue for future research is to disentangle the effects ofsocial support and SWB, recognizing that each can influence the other.2. Types of SWB. What types of SWB, for example, anger, affection, optimism, or lifesatisfaction, have effects on which physiological parameters? What is the structure of SWB thatprovides understanding of health outcomes? That is, which SWB variables are so highly relatedto one another that they provide no additional prediction of health beyond the others, and whichSWB variables provide independent health predictions? How long-lasting do moods andemotions have to be in order to affect health?3. Types of Health Outcomes and Subject Samples. What physiological systems andhealth outcomes does SWB most affect? When does SWB have little effect on health andlongevity, and when does it have large effects? For example, which diseases are relativelyimpervious to the effects of SWB. At what ages can SWB have the largest effects on healthoutcomes?A valuable addition to research on SWB and health would be to have measures ofpositive physical health, not simply measures of disease progression. Seligman et al. (2010) thefollowing concepts that may reflect positive health:Rapid wound healingLow blood pressureHigh heart rate variability

Much more research is required on the issue of what measures of positive health can reveal andwhether the assessment of positive health can reveal the effects of SWB prior to noticeableillness.We need more studies that follow people from young adulthood into old age, in order toassess the full impact of SWB on longevity, with less threat that initial health at baseline in thestudy was already compromised by low SWB. In the case of older samples, controlling forbaseline health could control away the earlier effects of SWB on health. We need research onmore varied populations, for example, more studies of those living in very difficult or stressfulsituations. Finally, we need studies of natural situations that can cause large differences in SWB.4. Interventions. At what levels of societal and individual SWB can interventions to raiseSWB benefit health? At what levels is SWB high enough so that increases will not influence

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health? Is the influence of SWB on health linear, convex, or concave? What types of SWBinterventions, whether individual or societal, are most likely to benefit health?Methodological RigorStudies in this field differ substantially in methodological rigor. One difference is in themeasurement of SWB. Some studies use simple single-item scales, which are bound to lowerreliability and attenuate correlations. Very few studies use measures of SWB besides self-report,such as reports by informants. Although survey self-report measures of SWB may be the bestsingle method of assessment we currently have, the advantage of adding other types of measuresis that they reduce concerns about overlapping method variance, for example when the healthoutcome itself depends to some degree on self-report. However, although the majority of workon SWB and health is based on self-report measures of SWB, not all is. For instance, Rosenkranzet al. (2003) found that negative affect as indexed by both right prefrontal brain activation andstartle response predicted poorer immune system strength.Smiling in photographs and ratings of autobiographies has been used to assess SWB. Inaddition, in studies of disasters such as earthquakes, and in experimental studies in which moodsare induced, the research design does not primarily rely on self-report measures of SWB. Finally,moods such as stress are inferred in many studies based on environmental factors such as testtaking or having a child with a disease. Thus, there is multi-method evidence supporting the linksof SWB to health. Furthermore, it is unlikely that biases in the self-report measures of SWBcould produce spurious effects in research using hard outcomes such as mortality. Althoughpersonality biases might slant self-reports of SWB and illness in similar directions, the majorityof outcome research does not depend on self-reports of health.

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More experimental studies are being implemented, including intervention research. Morestudies that follow large numbers of people over many years are being conducted. The rigor ofresearch has increased substantially since the early studies. There now are high quality studiesthat show effects equal or larger than studies of lesser quality (Cappelleri et al., 1996; Bausell,Lee, Soeken, Li, & Berman, 2004).One important issue is whether the effects of SWB on health are in fact due to inborndifferences between individuals that will not be susceptible to interventions. It could be thatfactors such as a genetic predisposition and early nutrition can influence SWB and alsolongevity, but that levels of SWB resulting from changing causes of SWB such as circumstancesor attitudes do not influence health. Countering this possibility are the findings that changedlevels of SWB are related to changes in physiology and health.Another issue is the fear that good health might cause both positive moods and laterhealth and longevity. Thus, SWB would be a result of underlying health (perhaps not captured bycurrent measures that focus on visible pathology), and not be a direct cause of future health.However, several types of data suggest that this cannot be the entire story. Experimental studiesof both humans and animals reveal that alterations in mood-relevant environments influencephysiological processes that are critical to health. The quasi-experiments show too thatenvironmental events can influence physiology that affects health. Finally, existing interventionstudies support the hypothesis that changes in SWB can influence health outcomes.Methodological rigor is of great importance to the field, and we should work to improveit. Early studies often suffered from small samples, low mortality, and brief follow-up periods(Kiecolt-Glaser et al., 2002). However, it must also be remembered that there are no perfect

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studies, even those that are considered state-of-the art. Thus, beyond the rigor of single studieswe need research by different investigators using different methods and samples.Statistical ControlThe difficulties of interpreting findings after instituting statistical controls areunderestimated by some researchers. Meehl (1970) and Kahneman (1965) explain the problemsinvolved in statistical control. Kahneman described the undercontrol that usually occurs becausemost variables are measured imperfectly. Conversely, Meehl described several of the unintendedtypes of overcontrol that can occur when statistical controls are employed, even thoughinvestigators are often unaware of the problems. First, when statistical controls are introduced forone factor, the sample becomes less controlled on other factors. Meehl calls this problemsystematic unmatching because when groups are statistically matched on one variable in thecausal sequence, they must be systematically unmatched on another variable in the causal chain.For instance, if you control SES in the predictions of school outcomes, because SES predictsbetter school outcomes and you want to hold it constant, you will have made the subjects lesssimilar on other input variables. If you equate children for reading ability after controlling forSES, for instance, it is likely that you will be comparing children who differ on other factorssuch as intelligence or motivation. Various methods of control, including regressions approachesand partial correlations, matching of individual subjects, and stratification, all suffer from similarshortcomings. A careful reading of Meehl is illuminating.The second problem when controls are introduced is that greater weighting is given tocertain less common subjects. In the example of SES, by statistical control you give less weightto subjects who are low or high on both SES and school performance, because the two are highlycorrelated, and give greater weight to those who are low in SES and high in performance, and

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conversely, those who are high in SES and low in performance. Obviously, a student who is froma high income and educated family and is performing poorly in school will be different from theaverage student in important ways, as will a student from a low SES family who is performing atan outstanding level. The problem is that statistical control has made the resulting groupsunrepresentative of the populations they are meant to represent.Finally, Meehl describes the issue of causal arrow ambiguity, an error based on themistaken idea that we can cleanly sort our variables into dependent and independent variables.We might assume that we know the causal relation between variables such as income and health,or SWB and SES, when in fact we do not. Often our subjects are to some degree self-selectedinto the very categories that many researchers want to control. Thus, we might be controllingaway a substantial finding by statistical overcontrol. If SWB influences income, marital status,and whether a person smokes, as well as health, we will be controlling away true SWB effects ifwe control these other variables. Meehls concerns do not imply that statistical controls shouldnever be undertaken, but they do mean that we must interpret the results carefully, and withknowledge of the pitfalls Meehl describes.An example of control may help reveal the complexities. If anger takes a progressive tollon cardiovascular health, and subjects are 50 years old on entry into a study, controlling health atage 50 will answer a different question from that provided when initial health at age 50 is notcontrolled, or when controlling health at age 20 occurs. By controlling health at age 50, whenanger might already have had a substantial detrimental impact, the researcher is probablyanalyzing whether anger after age 50 has an incremental or greater impact than prior anger. Evenif cardiovascular death is much more likely after age 50, anger before age 50 might already haveproduced substantial cardiovascular problems. Making matters even more challenging is the fact

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that anger and health may differ in stability and in the reliability with which they are measured.Thus, statistical controls must be introduced in a conceptually and psychometricallysophisticated way to produce interpretable results.An example of the use of statistical controls comes from research reported by KoivumaaHonkanen, Honkanen, Viinamaki, Kaprio, and Koshenvuo (2000). Following accepted practicesin the field, the authors controlled for factors such as marital status, social class, smoking,alcohol use, and physical activity, which reduced the association between life satisfaction anddisease-related deaths, and made the association inverse for women. However, these variablesare not simple confounds. Past research shows that the causal arrow cab move from SWB tofactors such as marriage and income. Positive affect and life satisfaction in many circumstancesincrease peoples likelihood of marrying, having high income, not smoking, and increasing theirprobability of exercising. Furthermore, these factors probably in turn influence SWB. Thecontrol variables and SWB are intricately intertwined in causal bidirectionality. Thus, controllingfor these factors might help illuminate the pathways mediating the connection going from SWBto health, but post-control findings showing no further association cannot be interpreted tosuggest that SWB does not cause health outcomes because SWB might have causally influencedthe control variables. In other words, smoking, marriage, and other factors must notautomatically be assumed to be biases or confounds, because they might be mediators of theSWB and health association.It is essential to carefully consider what statistical controls show. In the case of theKoivamaa-Honkanen et al. study the statistical controls were not inappropriate, but caution isneeded in interpreting the results. For example, Chida and Steptoes (2008) meta-analysis showsthe study as one with a large N in which SWB inversely predicted mortality. However, there

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were essentially no effects of SWB for women in the study before statistical controls wereinstituted. Thus, the results suggest that high and low SWB women lived about as long, but theylived less long when controlling for other variables, several of which are likely to be influencedby SWB. Further issues related to statistical controls, particularly in mediation analyses, arediscussed by Bullock, Green, and Ha (2010).Variations in Outcomes Across Types of SWBSubjective well-being is a broad category that includes diverse phenomena such as lifesatisfaction, positive affect, and low negative affect, such as infrequent sadness, anger, and fear.Suls and Bonde (2002) review the literature on various forms of negative emotions andcardiovascular diseases. They suggest that although depression is consistently related to impairedcardiovascular health, there is still much uncertainty about how specific negative emotions suchas depression, anxiety, and anger influence health in unison, in interaction, or independently.Keyes (2007) reports data showing that mental health is clearly more than the absence ofmental illness, suggesting that at the very least we must consider two factors to reflect SWB positive and negative. Most reviewers now conclude that positive and negative states produceindependent effects controlling for the other (e.g., Steptoe, Dockray, & Wardle, 2009). Forexample, Richman et al. (2005) found that people with hope had a lesser chance of experiencingdiabetes mellitus beyond the effects of negative emotions. Furthermore, in some instancespositive states have produced effects when negative states do not. Ignoring positive emotionsreflects a broad bias in the early days of this field. Pressman and Cohen (2005) suggest that somepast findings on negative affect and health might have in fact resulted from differences inpositive affect.

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In a meta-analysis of the literature, Howell, Kern, and Lyubomirsky (2007) found that illbeing slightly more strongly predicted short-term health outcomes, whereas positive well-beingslightly more strongly predicted long-term health outcomes, but in general the effects were ofsimilar size. We need not resolve the long-standing debate over the degree of independence ofpositive and negative emotions. It is sufficient that measures of the two types of emotions offerincremental predictions of health outcomes, perhaps because the two types of scales offerdifferential sensitivity to variations at different parts of the SWB continuum.Within the positive and negative categories, we can make finer differentiations. Forinstance, in the cardiovascular literature, some attempts have been made to differentiate thenegative effects of hostility versus sadness versus anxiety. Thus far it seems that bothanger/hostility and depressed mood, as well as severe depression, are detrimental tocardiovascular health. Nonetheless, more research is needed, including studies on negative affectthat also assesses positive states, as well as emotions' effects on other diseases.Types of positive states, such as optimism, joy, vigor, sociability, love, and contentmenthave not been clearly differentiated or measured in most research, and thus it is impossible todraw strong conclusions about what varieties of positive feelings are most beneficial to health,and at what levels. Marsland, Pressman, and Cohen (2007) discuss the fact that various statessuch as extraversion and optimism have not been clearly differentiated in terms of their healtheffects. They also suggest that highly aroused forms of positive emotions might have detrimentaleffects.One partition of SWB is into hedonic forms of happiness such as enjoyment of life versuswhat some have called, using Aristotles term, eudaimonic happiness (Vazquez, Hervas,Rahona, & Gomez, 2004). Eudaimonia refers to people developing their full potential, and

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therefore includes concepts such as mastery, meaning and purpose, and psychological growth.The distinction between hedonic and eudaimonic well-being is still being debated. Nonetheless,it will be useful to assess a wide range of states of psychological well-being in order to map theiroverlapping and independent contributions to health.In studies that compare multiple measures of well-being, it is important to equate themeasures for validity and reliability. Measures with different reliabilities, for example, could leadto spurious conclusions about the degree to which the underlying concepts are related to health,and therefore correcting for unreliability will be needed.Seligman et al. (2010) list types of positive psychological well-being, including:curiosity, hardiness, engagement, internal locus of control, sense of coherence, purpose, maritalsatisfaction, vitality, meaning, and mastery. To the Seligman et al. list we might add enjoyment oflife, low levels of anger and depression, contentment, happiness, work satisfaction, work strain,and life satisfaction. The possible list is virtually limitless because new concepts can be createdto describe nuanced differences in feelings and thoughts, as well as the situations that producethem. Clearly the proliferation of concepts will require pruning, and studies are needed thatinclude a broad examination of many measures, based on large and diverse samples, to determinehow the concepts are related to one another, and their independent ability to predict healthoutcomes beyond a general SWB factor score. Ideally, two or three different measures of eachconcept would be included so that latent trait scores might be created, and so that variance due topeculiarities of measures can be separated from the effects of the underlying constructs.Seligman et al. suggest that based on current evidence it is difficult to disentangle whichof the SWB concepts are most important. We are now in danger of multiplying conceptsindefinitely. Researchers must determine a structure of the basic SWB concepts that have

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separable effects on health. It might be that each of the myriad concepts of SWB can be reducedto several overarching concepts, and psychometric research is needed to accomplish this. In themeantime, new SWB concepts should be added cautiously until it can be demonstrated that theyadd prediction beyond highly studied concepts such as optimism, depression, life satisfaction,stress, and positive affect.Variations Across Populations and DiseasesIt is likely that SWB has different effects depending on the types of diseases beingconsidered, as well as the level of progression of the disease. After all, some diseases areprobably impervious to peoples moods. Like SWB, disease is an broad category covering manydifferent physiological processes, many different causes, and many levels of severity. There is noreason to believe that SWB would affect all types of illness to the same extent.It will not surprise anyone to learn that low SWB predicts mental problems and suicide.For instance, Bray and Gunnell (2006) found across 32 nations that happiness and lifesatisfaction were inversely associated with suicide rates. This is confirmed in studies ofindividuals, where SWB has been found to predict suicide (Koivumaa-Honkanen et al., 2001,2003). In addition, SWB strongly and inversely predicts accidents and deaths due tononintentional injuries (Koivumaa-Honkanen et al., 2000).The case of optimism and health shows the intricate patterns that can emerge whenanalyzing particular disease states and outcomes. It is likely that optimism is a beneficial factorin normal populations, and predicts all-cause mortality. However, a recent study byTomakowsky, Lumley, Markowitz, and Frank (2001) revealed that optimism among HIVinfected men was associated with poorer immune status.

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Segerstrom (2001, 2005) explains the mixed findings on optimism and health outcomes.Although this pattern has sometimes been explained by optimists being disappointed becausetheir expectations are unrealistically high for their medical conditions, she explains the pattern inreference to goal conflict. When optimistic people face goal conflict, they fare more poorly, butthey fare better when not facing such conflicts. Because optimists are more likely to stayengaged with goals and not withdraw from them, they have more short-term stress in the face ofgoal conflict. Segerstrom found support in two studies for this explanation, using immunemeasures as outcomes.Just as types of SWB and variations in disease states affect the SWB and health relation,so do the samples being considered. Among young adults health and resilience might be sostrong that few SWB effects on disease-related deaths are found. Similarly, very old peoplemight be so impaired and disease states so prevalent that SWB no longer predicts longevity.Similarly, levels of SWB might vary more in some groups, thus affecting the degree to whichSWB will predict health outcomes in these groups.An example of sample-specific findings is reported in the meta-analysis of Howell, Kern,and Lyubomirsky (2007) who found a strong and significant relationship between SWB andimmune functioning in healthy samples. This effect was much weaker and nonsignificant in theill. A number of such findings with differences in outcomes depending on the sample arereported in the tables. Rather than dismissing such findings as failures to replicate, suchdifferences can give us greater insight into the dynamics of SWB and health, as well as theboundary conditions involved in the relations.

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Dose-Response and Threshold Effects

There appears to be a dose-response relationship between SWB and health outcomes,such that serious depression is very bad, dysphoria is bad but less bad than depression, andpositive feelings are good (e.g., Giltay, Geleijnse, Zitman, Hoekstra, & Schouten 2004;Kubzansky et al., 2001), although there might be a ceiling of SWB beyond which increases arenot helpful.Several considerations lead us to inquire whether people can be too happy for it to benefittheir health, or whether certain types of happiness such as hypomania or highly aroused positiveaffect might even be detrimental to health. Oishi, Diener, and Lucas (2007) suggest thatachievement might be highest in the moderately happy, not in the super-happy. Supporting theidea that people might sometimes be too happy for their health, McCarron, Gunnell, Harrison,Okasha, and Davey-Smith (2003) found that hypomanic young men had greater risk ofcardiovascular mortality during the ensuing decades. Ritz and Steptoe (2000) found that extremepositive moods were associated with decreased pulmonary function.Pressman and Cohen (2005) suggest that those with diseases with high short-termmortality rates were harmed by high levels of PA (p. 960), whereas patients with longer termexpectations for survival may benefit or be unaffected by positive emotion. They write that,High levels of PA in seriously ill populations could be harmful because they are associated withthe underreporting of symptoms or overoptimistic expectations, both which could result infailure to seek medical care or adhere to physical advice. (p. 960). The authors conclude that ina few studies of the institutionalized elderly, higher rates of positive affect are related to higherrates of mortality.

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One study that stands out in prospective studies of SWB and longevity is Friedman et al.(1995) study of the Termites, the highly gifted children studied by Lewis Terman. They foundthat high cheerfulness was associated with greater mortality, running counter to the findings ofmost studies on positive feelings. However, the vast majority of the Terman sample was veryhappy, with few people at moderate or low levels of SWB. Thus, the correlation betweencheerfulness and longevity was primarily a comparison of the very happy with the extremelyhappy.Even if positive emotions have beneficial health effects, their benefits at high levels couldbe offset either by the physiological impact of high bodily arousal, or by the risks and activitiesundertaken by hypomanic and highly extraverted individuals. Such individuals might be morelikely to smoke, drink excessively, drive fast, and participate in other risky behaviors. Thus, atvery high levels positive feelings may lose their benefits.Although intense positive emotions might in some cases be harmful, below these levelsthere might be a dose-response relation between SWB and health, in the range from clinicaldepression up through contentment and moderately high levels of happiness. A dose-responsecurve between depressive symptoms and cardiovascular disease in the absence of majordepression (Rozanski, Blumenthal, & Kaplan, 1999) suggests that it is not just the lowest levelsof SWB that are harmful.Effect SizeEffect size estimates indicate how much of the variation in the dependent variable isassociated with differences in the independent variable. However, different effect size statisticsare used in different disciplines and for different types of measurement, causing some confusion.For example, odds-ratios or risk-ratios are often used in health studies to signify the differences

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between groups. For instance, an odds ratio of .80 for happy versus unhappy respondents andmortality would mean that 80 percent as many happy as unhappy subjects died during the studyperiod. In other instances effect size might be expressed in standard deviation units, or as amountof variance accounted for, and these indices are used when a graded measurement scale is usedfor SWB. Yet another metric for effect size is the number of life-years difference between groupsper unit of the independent variable. Given these different effect-size estimates, it is hard tomove quickly from one literature to another, and perhaps using several effect size estimates foreach study might be helpful in this cross-disciplinary field.When findings are statistically significant we may still inquire as to whether they are ofsufficient size to be of practical or policy significance. In a study of elderly Dutch over a 15-yearperiod, unhappy seniors had a mortality risk of 1.28 compared to happy respondents. In a studyof Finnish octogenarians (Lyrra, et al., 2006) the mortality risk for the quartile least satisfied withlife in terms of zest and mood was 1.80 compared to the most satisfied quartile. Kiecolt-Glaser etal. (2002) review studies on the size of effects on mortality for depression, anxiety, and anger.They conclude that the effects of depression on mortality are substantial, similar to the risk fromsmoking, hypertension, and diabetes. In patients suffering from acute coronary events, those withpanic-like anxiety had three times the risk of a fatal heart attack over a seven-year follow-upcompared to those without the anxiety.Lett et al. (2004) found that depression in otherwise healthy populations was a risk factorfor coronary artery disease of 1.5 to 2.0. In a meta-analysis of 40 studies, Chida and Steptoe(2008) found a psychological well-being risk ratio for mortality in healthy populations of .82,and a risk ratio in diseased population studies of .98. The risk ratio for mortality in healthypopulations over age 60 was .74. Thus, SWB was beneficial in healthy populations, with an

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effect size that is of sufficient magnitude to be of importance to public health. However, theeffect size found by Chida and Steptoe for mortality in diseased populations differed little from1.0.The effect sizes for SWB and specific causes of death can be lower or higher than theeffect sizes for all-cause mortality. For example, Koivumaa-Honkanen et al. (2002) reported thatthe risk ratio for dissatisfied compared to satisfied individuals for mortality due to injuries (bothintentional and nonintentional) was 2.8. The risk ratio of fatal nonintentional death was 7.8 fordissatisfied women and 4.0 for dissatisfied men, compared to their satisfied counterparts.How do the effect sizes compare with other lifestyle variables, which have been the focusof large public-health campaigns? Smith, Glazer, Ruiz, and Gallo (2004) conclude that theeffects sizes for hostility on cardiovascular disease are as large as those associated with manytraditional risks factors, and the associations are found even when a wide variety of potentialconfounding factors are controlled (p. 1239). Kvaavik, Batty, Ursin, Huxley, and Gale (2010)reported the strength of the association between healthy lifestyle behaviors and mortality. Forexample, the mortality risk for current smokers versus current nonsmokers was 1.52 and that forthose who frequently versus infrequently eat fruits and vegetables compared to those whofrequently eat them was 1.31. The risk for those doing none of the health behaviors was 3.49compared to those who scored in a positive direction on all four of them. However, theprediction of specific diseases varied. For example, eating little fruits and vegetables predictedcancer risk only 1.12. Kvaavik et al. estimated that those with all four positive health behaviorswould live 12 years longer than those who were low on all four, an estimate similar to the 14year estimate from Khaw et al. (2008).

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In terms of additional life-years, Veenhoven (2008) estimated that the effects of SWB onlongevity might be 7.5 to 10.0 years. Pressman and Cohen (2010) found that famouspsychologists who used positive emotion words in their autobiographies lived 4.2 years longerthan those who did not, while the use of negative words did not predict longevity. Howell, Kern,and Lyubomirsky (2007) estimated a 14 percent longevity difference between happy andunhappy individuals based on a meta-analysis of 24 studies. Using the average correlation in theanalysis and converting to standard deviation units, this could amount to six years difference inthe USA between individuals who are two standard deviations apart on SWB, or 75 years versus81 years life expectancy (Howell, 2010). Based on the age effects estimated from several reviewsand studies, an unhappy person in an economically developed nation might live 4-10 years lessthan a very happy person, recognizing that such an estimate depends on many factors.There is no underlying universal effect size for the association of SWB with health andlongevity. Effect sizes depend on the amount of variability of SWB in a population, exposure tovirulent pathogens, the length of the study, what ages subjects are observed, the reliability of theSWB measures, types of SWB assessed, and many additional factors. Thus, a single underlyingeffect size will not be discovered. This variability is clearly demonstrated in a study on theeffects of smoking (Doll, Peto, Wheatley, Gray, & Sutherland, 1994), in which British physicianswere assessed over a period of 40 years. Death rates due to smoking were double in the secondtwenty years compared to the first twenty years. Had the investigators followed subjects for 10years and controlled for initial health at the start of the study, effects would have been muchsmaller. Thus, the effects found in studies rarely give the full lifelong effects of lifestyle andpersonality factors. Nevertheless, the effects of SWB on accidents and suicides seem to be quitehigh, and for all-cause mortality the effects are similar to other lifestyle effects.

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Other IssuesAn important issue is whether the benefits of SWB for health found in the researchliterature are in part due to publication bias in which positive results are reported and analysesand studies in which nothing is found are less likely to be published. Several factors argueagainst this. First, several of the meta-analyses (e.g., Segerstrom & Miller, 2004; Hebert &Cohen, 1993) have analyzed the distributions of research findings, and concluded thatpublication bias is unlikely to produce the full effects found, although it might have some effect.In some analysis no evidence of publication bias has been discovered, and in others researchershave found find likely publication bias, but that an extremely large number of unreported studieswould be required to reverse the findings. Given the unsettled nature of this area, it seemsunlikely that huge numbers of negative findings are unreported. Indeed, one could imaginesituations in which methodologies that would be considered adequate in other areas of studywould be considered inadequate in this area, resulting in a negative editorial bias. Nevertheless,careful attention to the file-drawer problem is warranted.A related concern is that many investigators in studies with a large number of variablesanalyze many different associations, including SWB and health. When nothing is found, theresearchers move on to other questions, not wanting to waste time on nontrends. If this were tohappen frequently, then underreporting of null effects would occur without any intent on the partof investigators or journal editors to suppress null findings. This concern could be alleviated ifthere were a repository for null findings that would be quick and easy to use. This could helpreduce the file drawer problem. However, operating in the opposite direction is that for themajority of past studies in this field positive feelings were not assessed. Because positivefeelings seem to have substantial effects, and sometimes have effects when negative emotions do

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not, a large number of studies may have failed to find effects due to not assessing a key form ofSWB.SWB measures are usually substantially negatively skewed in normal populations, andmeasures of negative emotions are positively skewed. This should be considered when analyzingdata, for example into quartiles and so forth, as only one of the groups might differ in SWBsubstantially from the others, whose scores are relatively close together. The skewing of the dataraises the question of whether some transformation ought to be used, and requires attention wheninterpreting results.Originally skeptics broadly criticized the idea that SWB and psychosocial processescould influence health and longevity. However, as evidence has accumulated, much of theskepticism has narrowed to more specific questions. For instance, Coyne and Tennen (2010;Coyne, Tennen, & Ranchor, 2010) conclude that evidence is lacking that a fighting spirit orbenefit finding slow cancer progression. A decade ago skepticism that hostility could increasethe likelihood of heart diseases was expressed (e.g., Myrtek, 2001; Petticrew, Gilbody, &Sheldon, 1999), but more recent reviews have concluded that the case for the link is compelling(Smith, Glazer, Ruiz, & Gallo, 2004). Thus, over time skepticism focuses on the open questionsthat have not yet been answered in a clear and convincing way.Bjornskov (2008) expressed new skepticism about the benefits of happiness for health.He suggested that society-wide happiness might decrease longevity because happy societiesspend less on public health. In a sample of 15 economically developed European Union nationshe found that the average life satisfaction in the societies negatively predicted their public healthexpenditures. Following up on this suggestion in 95 diverse nations included in the Gallup WorldPoll, we found the opposite of what Bjornskov found in his small and homogeneous sample of

45

Health Benefits of Happiness

nations. We found that life satisfaction predicts longevity in nations after controlling per capitaincome, and we found that positive emotions predict a greater percentage of GDP is spent onhealth, controlling for GDP. We will report these findings in detail in a later paper, but it appearsto us that happy nations do not spend less on health or have shorter life expectancy.Take-Home MessageThere now are sufficient studies on all-cause mortality and some diseases to drawrelatively strong conclusions. Our overall conclusion is that the evidence for the influence ofSWB on health and all-cause mortality is clear and compelling, although there is much moreuncertainty about how various types of SWB influence specific diseases, and about the role ofthe possible mediating processes. The effect sizes for SWB and health are not trivial; they arelarge when considered in a society-wide perspective, and are not substantially different from theeffect sizes for several other health-relevant lifestyle variables. If high SWB adds four to tenyears to life compared to low SWB, this is an outcome worthy of national attention. When oneconsiders that the years lived of a happy person are more enjoyable and experienced with betterhealth, the importance of the SWB and health findings is even more compelling.Given the spiraling costs of medical care, healthy lifestyles are imperative. In light of theevidence it is perhaps time to add interventions to improve subjective well-being to the list ofpublic health measures, and alert policy makers to the relevance of SWB for health andlongevity. We need more research on what levels of SWB are required to produce benefits,although current evidence suggests that individuals in the low range for SWB would likelyexperience better health if their SWB could be raised.High subjective well-being is a state that many desire, some achieve, and a few despise asan unnecessary luxury or even a detriment. Given its clear and compelling relation to physical

Health Benefits of Happiness

health and longevity, we need to begin thinking of societal SWB as something that is indeeddesirable and beneficial.

Sample and Findings

Abel & Kruger

Blazer & Hybels

Deeg & van

Zonneveld

1989

Friedman et al.

1995

Giltay et al.

2004

Guven &Saloumidis

2009

Koopmans et al.

2010

Photographs of 196 professional baseball players taken in 1952

were rated for smiling. Mortality occurring by 2009 was predictedby smiling.1,250 coronary disease patients aged 46-58 were followed annuallyup to 19.4 years. Well-being and somatic symptoms significantlypredicted survival,4,162 subjects in North Carolina, aged 65-105, with 10-year followup. Positive affect, but not negative affect, was related to longevity.866 coronary disease patients with an average age of 60.3 werefollowed for about 11.4 years, during which time 415 deathsoccurred. The findings suggest that the relation between positiveemotion and mortality may be partly mediated by depressiveemotion.4,989 students who filled out an optimism scale at entry intouniversity in 1964-66 were followed for 40 years. Pessimisticindividuals had lower rates of longevity compared with optimisticindividuals.180 Catholic nuns wrote autobiographies at an average age of 22.Relation between the emotional content and survival was assessedat age 75-94. Nuns writing more positive autobiographies whenentering the convent in young adulthood lived longer than nunswriting less positive autobiographies.3,149 Dutch in a representative sample, aged 65-80 at baseline.Mortality was determined about 28 years later. Satisfaction withaging, income, and value of life were all related to longevity, evenafter controlling for symptoms and initial indicators of ill-health.The most cheerful of Termans gifted subjects had more healthproblems (more likely to smoke & drink) and survival analysisshows them to die younger.Dutch elderly 65 to 85, N of 941, 9-year follow-up. Optimismpredicted lower all-cause mortality, with a stronger effect for men inall-cause mortality but not cardiovascular mortality. Optimismpredicted cardiovascular mortality controlling for chronic disease,smoking, hypertension, obesity, cardiovascular disease, and alcoholconsumption. For both men and women there was a dose-responserelation between optimism and mortality.German Socioeconomic Panel Study, 1985-2007, N = 11,557Happiness predicted longevity more strongly for men and thechronically ill. The effects of marriage on longevity appeared to bemediated by happiness.861 Dutch elderly aged 65-85 in the Arnhem Elderly Study

Health Benefits of Happiness

Kubzansky et al.

2001

Loberiza et al.

2002

Lyrra et al.

2006

McCarron et al.

2003

Moskowitz et al.

2008

Moskowitz

2003

Ostir et al.

2000

Scherer &

2009

62

followed for all-cause mortality after 15 years. Happiness was

measured by reports of many happy moments and often laughinghappily. Happy respondents had a .78 hazard ratio (controlled forage and sex) of mortality compared to unhappy respondents, andthis persisted controlling for marital status and SES. In comparison,the hazard ratio for smoking was .72, and for number of diseaseswas .76. The relationship of happiness and longevity becamenonsignificant when physical activity, smoking, and chronic diseaseat baseline were controlled (although the hazard ratio remained .92for the happiest versus unhappiest tertiles).1,306 participants from the Greater Boston area, aged 21-80,followed for 12 years. Optimism predicted lower rates of heartattack and fatal coronary heart disease. A dose-response relation wasfound between optimism and each of the cardiac outcomes.Studied 193 patients receiving stem-cell transplants over a period oftwo years. Depressed patients had a threefold risk of dyingcompared to the nondepressed between 6 and 12 months after theoperation, controlling for other prognostic factors. After one year,surviving depressed patients were more likely to be takingmedications related to transplantation and less likely to be working.Scandinavian twin study, 320 respondents 80 years and older.Low current life satisfaction defined by zest and mood almostdoubled the risk for mortality in the low versus high quartiles.Controlling for depression, social functioning, and serious diseasesdid not reduce the life satisfaction effect.9,239 male students aged 16 to 30 were followed for an average of20.5 years. Anxiety predicted all-cause mortality and cancer risk(Cox risk ratios of 1.36 and 1.51, respectively). Hypomanic menhad an increased risk of cardiovascular mortality (Cox 1.90).715 diabetics and 2,673 comparison control subjects. Positive affectpredicted all-cause mortality in diabetics, and enjoyment predictedlower risk of mortality beyond the effects of negative affect in a 20years follow-up. Positive affect was not predictive of mortality inthe entire comparison sample, but enjoyment and hope werepredictive of lower mortality for those over age 65, and theypredicted beyond negative affect. Positive affect remainedpredictive when other predictors were controlled.407 HIV-positive people at baseline. Followed at 1, 2, and 3 years.Positive affect predicted mortality at one and two years, controllingfor various biological factors and negative affect.2,282 Mexican Americans aged 65 to 99, followed for 2 years.Subjects with high positive affect were half as likely to have diedduring the 2-year follow-up. Positive affect seemed to protectindividuals against physical declines (e.g. becoming disabled, slowwalking speed).575 hospitalized patients, followed for one year after discharge.

Health Benefits of Happiness

Hermann-LingenShirai et al.

2009

Tindle et al.

2009

Whang et al.

2009

Whooley &Browner

1998

Wilson et al.

2003

Xu

2005

Xu and Roberts

2010

63

Single-item measure of positive affect (enjoyment) predicted

survival, controlling for physician rated prognosis, co-morbidityscores, and hemato-oncological disease.88,175 Japanese adults, aged 50 to 69, free of cardiovasculardisease at baseline, were followed up on average after 12 years.Enjoyment of life was associated with lower risk of cardiovasculardisease, stroke, and cardiovascular mortality for men only.Followed 97,253 women for about 8 years in the Womens HealthInitiative who were initially free of cancer and heart disease.Optimists had lower mortality from heart diseases, fewercardiovascular events, and black optimists also had lower rates ofcancer related deaths. Women high in cynical hostility had highercancer mortality, cardiovascular problems, and overall mortality,with this effect being pronounced in blacks.63,469 nurses aged 30-55 at entry in The Nurses Health Studycohort followed every 2 years for about 30 years. Depressionpredicted fatal cardiovascular disease.Prospective study of 7,518 white women 67 years and older, fromseveral USA cities, were followed after 7 years, controlling formany diseases and cognitive functioning. Depression at T1 stronglypredicted all-cause mortality, cardiovascular death, andcardiovascular disease, but not deaths from cancer.Catholic clergy (N = 851) were followed for a mean of 4.7 years.Depression and suppressed anger were predictive of mortality, butanger at others was not. Those high in internally directed negativeaffect were nearly twice as likely to die as those who were low inthis characteristic.29-year Alameda County Study (USA) representative sample of6,928 subjects above the age of 20 at baseline. SWB was measuredby combining scores on life satisfaction, positive affect, and areverse score of negative affect. Subjective well-being reduced therisk of all-cause, natural-cause, and cardiovascular mortality.Positive feelings had an even stronger effect on these, and alsopredicted lower unnatural cause mortality (suicide, drugdependency, alcohol-related liver disease, etc.). Effects continuedafter controlling for demographics, initial health and obesity, andhealth practices. The effects of negative feelings did not continueafter the covariates were controlled.Same general sample as above, N of 6,856 were followed from1966 to 1993. The researchers controlled demographic and healthcovariates at baseline. Positive feelings, life satisfaction, anddomain satisfactions predicted lower risk of all-cause and naturalcause mortality, with risk ratios varying from .90 to .99. Positivefeelings and life satisfaction also predicted unnatural-causemortality (risk ratios running from .86 to .96). Associations foundboth in those younger and older than age 55. Results were strongest

Health Benefits of Happiness

in healthy subsamples. Mortality showed no association withnegative feelings. The positive findings seemed to be mediatedpartly or completely by social networks.

64

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Health Benefits of Happiness

Table 2: Longitudinal Studies of Illness and SWB

Authors

Year

Sample and Findings

Brummett et al.

2009

Collins et al.

2008

Davidson et al.

2010

Fitzgerald et al.

2000

Fredman et al.

2006

Freese, et al.

2007

Hamilton

1996

KoivumaaHonkanen et al.

2002

KoivumaaHonkanen et al.

2004

Nabi et al.

2008

Ostir et al.

2004

Ostir et al.

2001

948 hospitalized coronary artery disease patients followed for 3

years. Lower positive emotions at Time 1 were associated withquicker decline in functional status, while lower positive feelings atfollow-up were associated with decline only for men.3,363 Taiwanese near elderly and elderly were followed for 8 years.Mobility limitations were predicted by T1 life satisfaction andperceptions of future happiness only for those with no mobilitylimitations at T1, controlling for SES, health, social involvement anddepressive symptoms at baseline.1,739 Canadian adults in Nova Scotia, with 10-year follow-up.Positive affect predicted cardiovascular and ischemic heart disease.Increased positive affect was protective against 10-year incidentCHD.50 Caucasian CHD patients aged 38-77 followed 8 months aftersurgery. Dispositional optimism predicted decreased angina, positiveaffect, and risk-factor reduction.2-year study of 432 hip-fracture patients, aged 65 and older.High positive affect at Time 1 associated with faster walking andchair-stand speeds.Failed to find self-reported health differences in the WisconsinLongitudinal Study, with a 36 year follow-up, between those whosmiled and did not smile in high school yearbook photos (N = 3,007)Cancer patients, N = 213, were assessed 3 years after baseline.High positive mood predicted survival of lung cancer. Low levels ofnegative mood predicted survival of breast cancer.Finnish twins 18-54 years old, N = 29,173. Life satisfactionpredicted lower unintentional injury mortality after controls fordemographic and health behavior variables for both men andwomen.Finnish twins aged 18-54 years old, N = 22,136. Life satisfactionpredicted lower disability pensions from psychiatric andnonpsychiatric causes, especially among the healthy, and aftercontrols for demographics and health behaviors.10,308 civil servants aged 35 to 55 free of coronary heart disease atbaseline, in London, with a 12 year follow-up. Positive affect andaffect balance did not predict coronary heart disease. A weakpositive association was found between negative affect and coronaryevents.1,558 nonfrail older Mexican Americans were followed over 7 years.Positive affect lowered risk of future frailty.2,478 older North Carolina, adults over 6 years with no history of

Health Benefits of Happiness

Ringback et al.

2005

Seeman et al.

2002

Shen et al.

2008

Siahpush et al.

2008

Strik et al.

2003

66

stroke at baseline. Depression related to incidence of stroke,

controlling for T1 demographics, smoking, BMI, blood pressure andselected chronic diseases. Positive affect had a strong inverseincidence with stroke incidence.A representative sample of 34,511 Swedish persons aged 16 to 74followed at 5 and 10 years. High baseline anxiety and nervousnesspredicted suicide attempts, psychiatric illness, hospital care, andischemic heart disease, with stronger predictions for men.106 older adults aged 58-59 years old. Subjects reporting morepositive emotions with family and friends had fewer healthsymptoms and chronic conditions, and better subjective health.Those with fewer positive relationships had a higher allostatic load.735 older men in the Normative Aging Study, with no history ofheart disease or diabetes, were followed for 12.4 years. Controllingfor SES and other biological factors, anxiety predicted a greaterincidence of myocardial infarction (risk ratio of 1.43). The effectsremained after controlling for health behaviors, depression, hostility,and negative emotion.9,981 adult Australians were followed over 3 years. Happy and highlife satisfaction subjects had better physical health at 2 year followup, as well as absence of long-term limiting health conditions,controlling for baseline health and other covariates.Followed 318 male survivors of myocardial infarction for an averageof 3.4 years. Anxiety and depression predicted cardiac events afteradjusting for age and other factors. However, anxiety explainedaway the effects of depression on cardiac events. Anxiety was also apredictor of re-hospitalization and frequent outpatient visits.